genDeterministicUuidV4.kt

import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec
import kotlin.experimental.and
import kotlin.experimental.or

fun hmacSha256(data: String, key: String): ByteArray {
    val algorithm = "HmacSHA256"
    val secretKeySpec = SecretKeySpec(key.toByteArray(), algorithm)
    val mac = Mac.getInstance(algorithm)
    mac.init(secretKeySpec)
    return mac.doFinal(data.toByteArray())
}

fun genDeterministicUuidV4(data: String, key: String): String {
    val bytes = hmacSha256(data, key)

    // Per 4.4, set bits for version and 'clock_seq_hi_and_reserved'
    bytes[6] = (bytes[6] and 0x0f.toByte()) or 0x40.toByte()
    bytes[8] = (bytes[8] and 0x3f.toByte()) or 0x80.toByte()

    val stringBuilder = StringBuilder()

    for ((i, b) in bytes.withIndex()) {
        if (i == 16) break
        if (i == 4 || i == 6 || i == 8 || i == 10) {
            stringBuilder.append("-")
        }
        stringBuilder.append("%02x".format(b))
    }

    return stringBuilder.toString()
}

fun main() {
	println(genDeterministicUuidV4("00001", "henry-keiai-patient"))
	println(genDeterministicUuidV4("00002", "henry-keiai-patient"))

	println(genDeterministicUuidV4("00001", "henry-keiai-doctor"))
}